阅读说明：本技术 一种同时降低淀粉相对结晶度和热稳定性的方法 (Method for simultaneously reducing relative crystallinity and thermal stability of starch ) 是由 林日辉 樊艳叶 周丽红 曾艺君 于 2019-11-05 设计创作，主要内容包括：本发明公开了一种同时降低淀粉相对结晶度和热稳定性的方法,属于天然高分子材料制备及应用技术领域,将淀粉与醇盐溶液混合反应,在特定的反应条件下,能够对淀粉的溶胀解体问题得到有效抑制,在维持淀粉颗粒原有形貌的条件下有效降低了其结晶度,为进一步了解盐处理对淀粉结构的影响提供思路和依据。(The invention discloses a method for simultaneously reducing the relative crystallinity and the thermal stability of starch, belonging to the technical field of preparation and application of natural high polymer materials.)

1. A method for simultaneously reducing the relative crystallinity and the thermal stability of starch, comprising the steps of:

(1) selecting alcohol and mixing with salt to obtain alkoxide solution, wherein the salt is any one of lithium chloride, lithium nitrate, calcium chloride and calcium nitrate;

(2) weighing starch, placing the starch in a reaction kettle, dripping an alkoxide solution into the reaction kettle while stirring uniformly, and reacting to obtain starch milk;

(3) after the reaction is finished, naturally cooling the reaction kettle at room temperature, carrying out vacuum filtration on the starch milk in the reaction kettle, taking the filter cake to wash, and drying to obtain the product starch with reduced relative crystallinity and thermal stability.

2. The method for simultaneously reducing the relative crystallinity and the thermal stability of starch according to claim 1, wherein in step (1), the alcohol is ethanol; the volume concentration of the ethanol is 90-95%.

3. The method for simultaneously reducing the relative crystallinity and the thermal stability of starch according to claim 1, wherein in the step (1), the alkoxide solution contains lithium chloride with the concentration of 0.25-0.30mol/L or lithium nitrate with the concentration of 0.25-0.30mol/L or calcium chloride with the concentration of 0.10-0.15mol/L or calcium nitrate with the concentration of 0.10-0.15 mol/L.

4. The method for simultaneously reducing the relative crystallinity and the thermal stability of starch according to claim 1, wherein in step (2), the starch is tapioca starch or corn starch.

5. The method for simultaneously reducing the relative crystallinity and the thermal stability of starch according to claim 1, wherein in the step (2), the dosage ratio of the starch to the alkoxide solution is 1 g: 14-16 ml.

6. The method for simultaneously reducing the relative crystallinity and the thermal stability of starch according to claim 1, wherein in the step (2), the reaction process is carried out in a drying oven at 110-120 ℃ for 3-4 h.

7. The method for simultaneously reducing the relative crystallinity and the thermal stability of starch according to claim 1, wherein in the step (3), the washing method is performed 2-3 times by using ethanol with a volume concentration of 95-97%.

8. The method for simultaneously reducing the relative crystallinity and the thermal stability of starch according to claim 1, wherein in the step (3), the drying process is carried out in a drying oven at 35-37 ℃ for 12-16 hours.

9. The product starch obtained by the process of any of claims 1 to 8, wherein the product starch has a crystallinity of as low as 15.86% and an amylose content of as low as 22.42%.

Technical Field

The invention belongs to the technical field of preparation and application of natural high polymer materials, and particularly relates to a method for simultaneously reducing relative crystallinity and thermal stability of starch.

Background

Starch, as the most abundant natural polymer after cellulose, has the advantages of low price, reproducibility, biodegradability and the like, and is widely applied to the fields of food, textile, paper making, medicine and the like. However, the use of starch is somewhat limited due to its complex semi-crystalline structure. To improve the function and properties of starch, the starch may be modified by physical, chemical, and enzymatic methods.

Properties of salt on starchThe method has obvious effect, the effect depends on the concentration and the type of anions/cations, and researches show that when a digital image analysis method is used for researching the gelatinization process of a starch/sodium chloride solution system, the influence of sodium chloride with different concentrations on the gelatinization process of corn starch, potato starch and pea starch is different, the influence of salt ions on the gelatinization and retrogradation characteristics of the corn starch and the waxy corn starch follows Hofmeister series, namely the anion sequence is SCN^->I^->NO₃ ^->Br^->Cl^->SO₄ ^2->F^-The cation being Li⁺>Na⁺>K⁺。

There are relatively few reports of the effect of salt on starch structure compared to studies of the effect of salt on starch properties. It was found that the morphology of the starch granules changed after treatment with 4M or 4.4M calcium chloride solution at room temperature. After treatment with 13M lithium chloride solution at room temperature, gelatinization occurred on the surface of the corn starch granules. The research is carried out in aqueous solution, and starch granules are easy to swell and disintegrate, so that the subsequent treatment process becomes complicated. Meanwhile, because the polarity of water is very high, the existence of a large number of water molecules can generate strong interference on the action of salt ions. The Chinese patent with publication number CN109908396A, a calcium ion exchange porous starch hemostatic material, a preparation method and application thereof, discloses starch, an oil phase, a pore-forming agent, an emulsifier, calcium chloride and the like as raw materials, and specifically discloses a plurality of components such as cassava starch, sweet potato starch, calcium chloride, ethylene glycol, ethanol and the like; the realization of the starch structure provides porous adsorption properties.

In order to solve the above problems, further research on the influence of salt treatment on the starch structure is needed, and the problem that starch granules are easy to swell is solved.

Disclosure of Invention

In order to solve the problems, the invention provides a method for simultaneously reducing the relative crystallinity and the thermal stability of starch, which uses alcohols as a solvent and utilizes salts such as lithium chloride, lithium nitrate, calcium chloride and calcium nitrate to treat the starch, can effectively inhibit the swelling and disintegration problem of the starch, effectively reduces the crystallinity of starch granules under the condition of maintaining the original appearance of the starch granules, and provides ideas and bases for further understanding the influence of salt treatment on the structure of the starch.

In order to achieve the purpose, the scheme provided by the invention is as follows:

a method for simultaneously reducing the relative crystallinity and the thermal stability of starch, comprising the steps of:

(1) preparing and selecting alcohol and mixing with salt to obtain alkoxide solution, wherein the salt is any one of lithium chloride, lithium nitrate, calcium chloride and calcium nitrate;

(2) weighing starch, placing the starch in a reaction kettle, dripping an alkoxide solution into the reaction kettle while stirring uniformly, and reacting to obtain starch milk;

(3) and after the reaction is finished, naturally cooling the reaction kettle at room temperature, carrying out vacuum filtration on the starch milk in the reaction kettle, taking the filter cake to wash, and drying to obtain the product starch with reduced relative crystallinity and thermal stability.

Further, in the step (1), the alcohol is ethanol; the volume concentration of the ethanol is 90-95%.

Further, in the step (1), the alkoxide solution contains lithium chloride of 0.25 to 0.30mol/L concentration, lithium nitrate of 0.25 to 0.30mol/L concentration, calcium chloride of 0.10 to 0.15mol/L concentration, or calcium nitrate of 0.10 to 0.15mol/L concentration.

Further, in the step (2), the starch is tapioca starch or corn starch.

Further, in the step (2), the use amount ratio of the starch to the alkoxide solution is 1 g: 14-16 ml.

Further, in the step (2), the reaction process is carried out in a drying box at the temperature of 110 ℃ and 120 ℃ for 3-4 h.

Further, in the step (3), the washing method is performed 2 to 3 times by using ethanol with a volume concentration of 95 to 97%.

Further, in the step (3), the drying process is carried out in a drying oven at 35-37 ℃ for 12-16 hours.

The crystallinity of the starch of the product obtained by the method is as low as 15.86 percent, and the content of amylose is as low as 22.42 percent.

The raw materials used in the invention are as follows: tapioca starch, corn starch, lithium chloride, lithium nitrate, calcium chloride, calcium nitrate, ethanol and the like are purchased from chemical raw material companies at home and abroad, and are directly used without being continuously purified.

The principle of the invention is as follows:

according to the method, alcohols are used as a solvent, salts such as lithium chloride, lithium nitrate, calcium chloride and calcium nitrate are used for treating starch, ions enter the interior of starch granules and interact with molecular chains of the starch, so that the ordered arrangement of the molecular chains of the starch is broken, the original crystal structure of the starch is reduced, the original ordered arrangement among the molecular chains of the starch is broken, the crystallinity of the starch granules is effectively reduced under the condition of maintaining the original appearance of the starch granules, the salt ions can also enter the interior of the starch granules and generate electrostatic interaction with water molecules, the activity of the water molecules is reduced, the strength of the interaction between the starch chains and the water molecules is weakened, the internal structure of the whole starch granules becomes loose, and the high thermal stability of the starch can be obviously reduced; the added alcohol solvent has the function of inhibiting the swelling of the starch, and can effectively inhibit the swelling and disintegration of the starch.

The invention has the following beneficial effects:

1. the preparation method of the invention uses alcohols as solvent, salts lithium chloride, lithium nitrate, calcium chloride and calcium nitrate are used for processing starch, salt ions can enter the interior of starch granules to interact with molecular chains of the starch and generate electrostatic interaction with water molecules, thereby breaking the ordered arrangement of the molecular chains of the starch, reducing the original crystal structure of the starch, destroying the original ordered arrangement among the molecular chains of the starch, and effectively reducing the crystallinity of the starch granules under the condition of maintaining the original appearance of the starch granules.

2. The product obtained by the preparation method has the crystallinity as low as 15.86 percent and the amylose content as low as 22.42 percent.

3. The invention can also reduce the activity of water molecules, thereby weakening the strength of the interaction between starch chains and the water molecules, loosening the internal structure of the whole starch granule and obviously reducing the high thermal stability of the starch.

4. The added alcohol solvent has the function of inhibiting the swelling of the starch, and can effectively inhibit the swelling and disintegration of the starch.

Drawings

FIG. 1 is an electron microscope scanning image of the product of the present invention.

FIG. 2 is an electron microscope scanning image of the raw material starch of the present invention.

FIG. 3 is a confocal laser microscopy of a product of the invention.

FIG. 4 is a laser confocal microscopic observation of the raw starch of the present invention.

FIG. 5 is an X-ray diffraction pattern of a product of the present invention.

FIG. 6 is an FTIR spectrum of a product of the present invention.

FIG. 7 is a thermogravimetric analysis of the starting starch of the present invention.

FIG. 8 is a thermogravimetric analysis of the product of the present invention.

In fig. 5 and 6, a is a raw material starch map, b is a product map of example 1, c is a product map of example 2, d is a product map of example 3, and e is a product map of example 4.

Detailed Description

The invention is further described with reference to the following examples: